package com.explorati.LinkedList.stack;

public class LinkedList<E> {

	private class Node {
		public E e;
		public Node next;

		public Node(E e, Node next) {
			this.e = e;
			this.next = next;
		}

		public Node(E e) {
			this(e, null);
		}

		public Node() {
			this(null, null);
		}

		@Override
		public String toString() {
			return e.toString();
		}
	}

	private Node dummyHead;
	private int size;

	public LinkedList() {
		dummyHead = new Node(null, null);
		size = 0;
	}

	// 获取链表中的元素个数
	public int getSize() {
		return size;
	}

	// 返回链表是否为空
	public boolean isEmpty() {
		return size == 0;
	}

	// 在链表头添加新的元素e
	public void addFirst(E e) {
		// Node node = new Node(e);
		// node.next = head;
		// head = node;
		add(0, e);
	}

	// 在索引为index的位置添加元素e
	// 关键：找到要添加节点的前一个节点
	public void add(int index, E e) {
		if (index < 0 || index > size) {
			throw new IllegalArgumentException("add failed, Requires index >= 0 && index <= size.");
		}
		Node prev = dummyHead;
		for (int i = 0; i < index; i++) {
			prev = prev.next;
		}
		// Node node = new Node(e);
		// node.next = prev.next;
		// prev.next = node;
		prev.next = new Node(e, prev.next);
		size++;
	}

	public void addLast(E e) {
		add(size, e);
	}

	public E get(int index) {
		if (index < 0 || index >= size) {
			throw new IllegalArgumentException("Get failed. Illegal index.");
		}
		Node cur = dummyHead.next;
		for (int i = 0; i < index; i++) {
			cur = cur.next;
		}
		return cur.e;
	}

	public E getFirst() {
		return get(0);
	}

	public E getLast() {
		return get(size - 1);
	}

	public void set(int index, E e) {
		if (index < 0 || index >= size) {
			throw new IllegalArgumentException("Set failed. Illegal index.");
		}
		Node cur = dummyHead.next;
		for (int i = 0; i < index; i++) {
			cur = cur.next;
		}
		cur.e = e;
	}

	public int find(E e) {
		Node cur = dummyHead.next;
		for (int i = 0; i < size; i++) {
			if (cur.e.equals(e)) {
				return i;
			} else {
				cur = cur.next;
			}
		}
		return -1;
	}

	public boolean contains(E e) {
		int i = find(e);
		if (i == -1) {
			return false;
		} else {
			return true;
		}
	}

	public E remove(int index) {
		if (index < 0 || index >= size) {
			throw new IllegalArgumentException("remove failed. Index out of bound.");
		}
		Node prev = dummyHead;
		for (int i = 0; i < index; i++) {
			prev = prev.next;
		}
		Node delNode = prev.next;
		prev.next = delNode.next;
		delNode.next = null;
		size--;
		return delNode.e;
	}

	public E removeFirst() {
		return remove(0);
	}

	public E removeLast() {
		return remove(size - 1);
	}

	@Override
	public String toString() {
		StringBuilder res = new StringBuilder();

		// Node cur = dummyHead.next;
		// while (cur != null) {
		// res.append(cur + "->");
		// cur = cur.next;
		// }
		for (Node cur = dummyHead.next; cur != null; cur = cur.next)
			res.append(cur + "->");
		res.append("NULL");

		return res.toString();
	}

}
